No, we should avoid developers who hold such incredibly wrong opinions.
In many cases, a database join is several orders of magnitude faster than anything done via the client, because it avoids DB roundtrips, and the DB can use indexes to perform the join.
Off the top of my head, I can’t even imagine a single scenario where a correctly used join would be slower than the equivalent client-side operation.
Edit: There are some rare cases where custom client code can do things more efficiently than a straightforward DB join (see comment by meriton). But this is very much the exception.